Emergency responders move heavy equipment near the scene of a shooting Tuesday in Jersey City, N.J. Six people, including a police officer and three bystanders, were killed. The dead also included the two suspects.

JERSEY CITY, N.J. — Six people, including a police officer and three bystanders, were killed in a furious gunbattle Tuesday that filled the streets of Jersey City with the sound of heavy fire for hours, authorities said.

The dead included the two gunmen, Jersey City Police Chief Michael Kelly said.

The slain officer, Detective Joseph Seals, 40, was credited by his superiors with having led the department in the number of illegal guns removed from the streets in recent years, and might have been trying to stop an incident involving such weapons when he was cut down by gunfire that erupted near a cemetery, authorities said.

The shooting then continued at a kosher supermarket about a mile away, where five more bodies were found, Kelly said.

“It’s a really tough day for the city of Jersey City,” Mayor Steven Fulop said. Seals “was one of the best officers for getting the most guns off the streets. He was a good cop.”

Two other officers were wounded but were later released from the hospital, authorities said.

The bullets started flying early in the afternoon in the city of about 270,000 people, situated across the Hudson River from New York City. Seals, who worked for a unit called Cease Fire, was shot around 12:30 p.m. The gunmen then traveled to another part of the city in a stolen rental van and engaged police in a lengthy shootout.

“Our officers were under fire for hours,” the chief said.

Inside the grocery store, police found the bodies of what they were believed were the two gunmen and three other people who apparently happened to be in the place when the assailants rushed in, authorities said. Police said they were confident the bystanders were shot by the gunmen and not by police.

The kosher grocery is a central fixture in a growing community of Orthodox Jews who have been moving to Jersey City in recent years. Authorities were unable to say why the gunmen went there.

Rabbi Moshe Shapiro, who shops at the kosher store and attends a synagogue next door, said he spoke with the store owner, Moishe Ferencz.

“He told me he had just walked out of the store into the synagogue not five feet away just before this happened, and then he couldn’t get back for hours,” Shapiro said. “His wife was inside the store. He said, ‘I hope my wife is safe.’”